1. Field of Invention
This invention relates to flux cored welding electrodes for use in gas-shielded electric arc welding and hard surfacing.
2. Summary of the Prior Art
In open-arc welding of steel it is known to use a tubular welding electrode filled uniformly throughout its length with a powdery mixture of slag-forming, deoxidising and arc stabilising substances and, on occasion, metal powders. The nature and proportions of the respective ingredients used depend upon the desired conditions of use; for most welding applications it is customary to employ a core having at least 20% by weight of the core material ingredients other than metal powders, whereas in hard surfacing applications more metal powder is normally used. The inclusion of iron powder in the core is advantageous in that it helps to increase the rate at which weld metal is able to be deposited from the electrode. In general, it is found that commercial flux-cored welding electrodes of the high metallic hardfacing types have the disadvantages of producing a great deal of spatter during use and of forming a scaly slag which is difficult to remove. In addition they frequently produce welds of poor shape. Electrodes having a higher flux content often suffer from the disadvantage that they deposit weld metal at a rate which is less than ideal.
Certain arc welding electrodes have been proposed which contain relatively small proportions of inorganic compounds which act as fluxing agents, slag forming agents and arc stabilisers. For example U.S. Pat. No. 3,787,658 describes flux-cored electrodes for producing ferrous weld deposits when employed as the consumable electrode in a short-circuiting arc welding process, the electrodes typically containing less than 1% (by weight of the total electrode) of inorganic compounds, from 1 to 2.5% by weight of manganese, less than 0.9% by weight of silicon and a core that constitutes from 10 to 15% by weight of the electrode.
U.S. Pat. No. 3,177,340 relates to flux-cored electrodes for use in an electrogas welding process. The electrodes typically have a core containing less than 1% by weight of the total electrode of inorganic compounds and unspecified quantities of other ingredients.
UK patent specification No. 1,056,804 relates to flux-cored arc welding electrodes for use in gas-shielded arc welding. In order to improve upon the efficiency during welding of conventional electrodes this specification recommends a core composition containing silica and titanium dioxide, the total weight of these ingredients constituting at least 3.5% by weight and at the most 9% by weight of the total weight of the welding electrode.
UK patent specification No. 1,071,149 relates to flux-cored arc welding electrodes for use in gas-shielded arc welding. The electrodes typically contain from 1 to 9% by weight of the total electrode of alkaline earth carbonate and alkaline earth fluoride. In addition the electrodes typically contain from 1.5 to 2.0% by weight of manganese and less than 1% by weight of silicon.
UK patent specification No. 1,123,926 relates to flux-cored electrodes for automatic or semi-automatic arc welding. The electrodes typically contain less than 1% by weight of inorganic compounds and are highly deoxidised which suggest that the electrodes are intended for use without an externally supplied shielding gas.